GENETIC VARIATION IN APHANIZOMENON (CYANOBACTERIA) COLONIES FROM THE BALTIC SEA AND NORTH AMERICA

Aphanizomenon Morren is an important member of the cyanobacterial community in the Baltic Sea, but studies of this genus have been hampered by the difficulty of growing it in laboratory culture. PCR amplification of DNA from colonies picked directly from water samples has circumvented this problem and made it possible to carry out an analysis of genetic diversity within the Baltic Sea and in two small North American lakes separated by just a few kilometers. The nucleotide sequence of the phycocyanin intergenic spacer and partial flanking coding regions of cpcB and cpcA was determined for 32 colonies of Aphanizomenon , 26 from the Baltic Sea, and 6 from the North American lakes. No variation was detected among the 26 Baltic Sea colonies, but two alleles, differing at 19 nucleotide positions (5.4%), were found in the North American lake colonies. Surprisingly, the two North American types were less closely related to each other than to the Baltic Sea genotype. The Baltic Sea Aphanizomenon is clearly distinct from A. flos-aquae at both the cpcB–cpcA and 16S rDNA loci, which lends phylogenetic support to their tentative separation based on ultrastructural analysis. We conclude that although there is significant genetic diversity in the genus Aphanizomenon , the population in the Baltic Sea is, in contrast to the Nodularia population, genetically homogeneous.     

A MOLECULAR AND PHENOTYPIC ANALYSIS OF NODULARIA (CYANOBACTERIA) FROM THE BALTIC SEA

The filamentous diazotrophic cyanobacterium Nodularia forms water blooms each year in the Baltic Sea. Filaments isolated from such water blooms vary in their trichome width, degree of coiling, and properties of their gas vesicles; previously, these characters have been used to classify individuals to species level. To test the validity of such a phenotypic classification, we determined the nucleotide sequences for a region of the phycocyanin locus that includes a noncoding intergenic spacer (PC-IGS), the IGS between two adjacent copies of the gvpA gene (which encodes the main structural gas vesicle protein) and the rDNA internal transcribed spacer (rDNA-ITS), for 13 clonal Nodularia isolates from the Baltic Sea during August 1994. The complete 16S-rDNA sequence was determined for three isolates and was found to be identical in each of them. Molecular sequences for noncoding regions of the genome were used to assign isolates to three groups on the basis of PC-IGS, two groups on the basis of gvpA -IGS, and three groups on the basis of rDNA-ITS. No consistent correlation was found between genotype and any of the phenotypic features examined, and no link was found between any of these features themselves, indicating that these characters are not useful for placing Nodularia isolates into meaningful taxonomic groups. The PC-IGS, gvpA -IGS, and rDNA-ITS genotypic groupings were not congruent. This might indicate that gene flow occurs between individuals in Nodularia populations.     

黄海中北部不同断面鱼卵、仔稚鱼群落结构特征

为了解黄海中北部近岸海域不同断面的鱼卵、仔稚鱼群落结构特征,基于2017年5月、6月和7月对黄海中北部近岸海域内不同断面表层水平拖网的调查数据,对该海域鱼卵和仔稚鱼的种类组成、数量分布、多样性等进行分析。结果表明:3个航次共采获鱼卵5493粒,仔稚鱼43尾,经鉴定共20种,隶属于7目16科20属,种类以鲈形目为主要类群。采获鱼卵、仔稚鱼的数量在不同月份和不同断面间有所差异,总体来看数量分布不均匀。采获鱼卵、仔稚鱼对应成鱼的适温类型主要由暖温种和暖水种组成,仅有少量冷温种,各生态类型种类数随断面不同有所变化,暖温种在调查海域内由北向南呈递减的趋势,暖水种则呈递增的趋势。鱼卵、仔稚鱼优势种和重要种组成在不同月份和不同断面间均有所差异,鳀(Engraulis japonicus)为5月航次调查海域及T1和T2断面的鱼卵优势种,仔稚鱼没有出现优势种。3个航次采集的鱼卵、仔稚鱼对应成鱼平均营养级分别为3.58、3.51和3.41,呈现逐渐降低的趋势。调查海域内鱼卵、仔稚鱼的丰富度指数(D)、多样性指数(H′)和均匀度指数(J′)均以5月航次最高, 6月航次最低。此外,两个断面各站位之间的丰富度指...     

REPRODUCTIVE SUCCESS OF FUCUS VESICULOSUS (PHAEOPHYCEAE) IN THE BALTIC SEA

Marine organisms colonizing brackish habitats such as the Baltic Sea must cope with the negative effects of low salinities on reproductive success because these may reduce gamete viability and/or increase polyspermy. Reproductive characteristics of the marine seaweed Fucus vesiculosus L. were studied in several brackish habitats, particularly in the northern Baltic Sea, to understand its ability to reproduce where few other marine species survive. Polyspermy and fertilization success were variable at the boundary of the continuous distribution of F. vesiculosus in the Baltic Sea, and polyspermy was high (10%–30%) when fertilization was successful. A strong female bias (80%–86%, ca. 5.5:1) was found at the northernmost limit of Baltic F. vesiculosus. Electrophysiological studies showed that many eggs have a high input resistance (519 ± 150 MΩ[mean ± SE, n = 14] at Drivan, 1995), which may be helpful in preventing polyspermy in this brackish habitat. The polyspermy block remains sodium-dependent in the northern Baltic. Sperm bound quickly to northern Baltic eggs in natural water, but fertilization was delayed compared to marine F. vesiculosus. A subset of northern Baltic eggs studied during an optimal reproductive period (7–11 July 1995) had a membrane potential (E_m) of ca. −100 mV and an effective fertilization potential (FP) of ca. 2 min with a plateau of −25 mV, but repolarized too rapidly for the FP to be protective. Pronuclear migration and cell wall secretion occurred more slowly in Baltic than in marine zygotes. The reproductive success of theseboundary populations may be dependent upon windows of opportunity when there are favorable combinations of the levels of salinity, water motion, population density, and sex ratio. These factors and the short duration of the reproductive season in the northern Baltic Sea may result in reproductive failure in some years.     

COASTAL DIATOM–ENVIRONMENT RELATIONSHIPS FROM THE GULF OF FINLAND,BALTIC SEA1

Eutrophication of the Baltic Sea has become a serious concern in recent decades. To provide a potential means for quality assessments of coastal waters in this area, we collected a data set of 49 embayments in the Gulf of Finland, and explored the relationship between surface sediment diatom assemblages and 15 environmental variables, with special emphasis on nutrients. Total dissolved nitrogen, total phosphorus, depth, and salinity all accounted for significant and independent fractions of variation in the diatom data and explained 34% of the total variation. There were clear changes in diatom assemblage structures along the nutrient gradients. Although these changes were gradual, we could identify a number of taxa that were more abundant in a particular nutrient environment. These taxa could be used as potential indicators of the quality of coastal waters in the Baltic Sea. Diatom assemblages that were least affected by nutrient enrichment included a variety of benthic species and a relatively high species richness. Small planktonic taxa such as Cyclotella atomus Hustedt, Cyclotella meneghiniana Kützing and Thalassiosira pseudonana Hasle and Heimdal were good indicators of highly elevated nutrient concentrations (>600 lg·L^?1 total dissolved nitrogen and 60 lg·L^?1 total phosphorus) together with low species richness. The first appearance of these small planktonic taxa in regular monitoring could be used as an early warning sign for deteriorating water quality. Diatoms could be applied to water quality classification and monitoring purposes in the coastal waters of the Baltic Sea area using techniques such as weighted‐averaging regression and calibration.     

LOCAL ADAPTATION OF CERAMIUM TENUICORNE (CERAMIALES,RHODOPHYTA) WITHIN THE BALTIC SEA1

Ceramium tenuicorne (Kützing) Wærn is a red alga that is widely distributed in the brackish Baltic Sea. We studied the growth response of Ceramium to low salinity and nutrient enrichment, using isolades from two regions of the Baltic Sea where the alga approaches its inner distribution limit. Ecotypic differentiation was observed in that differences in growth response among isolates corresponded to salinity conditions in their regions of origin. Isolates from the Gulf of Bothnia (4 psu) had inherently lower growth rates that were not increased when transferred to higher salinity, but were better adapted to very low salinity levels than isolates from the Baltic Proper (7 psu). Further, the results indicate that Ceramium from different regions of the Baltic Sea vary in their responses to nutrient enrichment. The observed differences may be best described as a quantitative difference in the proportion of isolates with hyposaline adaptation. The results indicate that the wide distribution of Ceramium in the Baltic Sea is better explained by the occurrence of locally adapted genotypes than by a generalist life strategy, and provide example of adaptive differentiation in a marine edge environment.     

THE ASSESSMENT OF COMPETITION BETWEEN SEALS AND COMMERCIAL FISHERIES IN THE NORTH SEA AND THE ANTARCTIC1

Most of the exploited fish stocks in the North Sea are also used as a food supply by a number of seal species; the same is true for some fish and invertebrate stocks in the Antarctic—although the fisheries there are, at present, much smaller than those in the North Sea. The information needed for a critical assessment of such interactions is reviewed. Using existing techniques it is possible to estimate the quantity and size-classes of each fish or invertebrate species consumed by seals and to compare this with the commercial catch. If fishing mortality is known, these estimates can be used to calculate the level of mortality imposed by the seals. However, a realistic evaluation requires information on the distribution and movements of the fish, the seals' feeding effort, and the fisheries effort in time and space. At present it is difficult or impossible to obtain this information, but recent technological developments in telemetry equipment will soon make it feasible. To assess the economic effects of changes in seal numbers on the fishery, or the ecological effects of changes in fisheries effort on seal populations, requires additional information on the responses of the fishery and the seals to changes in fish abundance, and of the commercial market to changes in the supply of fish.     

寰椎的测量、相关与性别判别分析

本文对85例(男46,女39)国人寰椎进行了四项测量,其性差均非常显著,但两性重迭率≥38.9％。另算出两项指数,其性差不显著。从中挑选全宽(X_1)和矢径(X_2)两个变量经计算得判别式Z=X_1+2.21098x_2,临界值Z_0=172.9102。经组内外回代误判率分别为18.5％和12.9％。对四项测量作了相关分析,其中寰椎矢径与椎孔横径、全宽与椎孔矢径均呈中度正相关。并用寰椎矢径(X_2)推算椎孔横径(y),其男性Y=18.01±0.2579X_2,女性Y=4.88±0.5505X_2。     

唐山湾海域鱼类分类多样性研究

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SUMMER DISTRIBUTION OF PICOPHYTOPLANKTON IN THE NORTH YELLOW SEA

 利用荧光显微技术(Epifluorescence microscopy, EFM)对2006年夏季北黄海水域80个站点的微微型浮游植物进行了检测, 并对其在平面和垂直分布上的变化以及昼夜变化情况进行了研究。检测到聚球藻(Synechococcus, Syn)和真核球藻(Picoeukaryotes, Euk)两类微微型浮游植物, 未检测到原绿球藻(Prochlorococcus, Pro), 其中Syn以富含藻红素的Syn细胞(PE细胞)为优势种类, 而富含藻蓝素的Syn细胞(PC细胞)数量较少。在荣城湾以东的水域, 各水层Syn和Euk的丰度都较其它水域的高。Syn在北黄海冷水团及附近水域下30 m深处和底层水体中出现明显的低值区, Euk丰度受冷水团影响不明显。在垂直分布上, 水表层和水下10 m深处Syn的丰度高于水下30 m深处和底层, 而Euk在垂直分布上无明显差异。在昼夜变化上, 各水层Syn、Euk丰度的白昼与夜间变化趋势无明显区别。     

ALLOXANTHIN IN DINOPHYSIS NORVEGICA (DINOPHYSIALES, DINOPHYCEAE) FROM THE BALTIC SEA

The pigment composition of Dinophysis norvegica Ehrenberg from the central Baltic Sea differs from the normal pigment pattern found in dinoflagellates, which contain peridinin as a typical marker pigment. In D. norvegica isolated by cell fractionation of field samples, the major carotenoid was alloxanthin, a typical cryptomonad pigment. No evidence was found that the presence of alloxanthin was due to a recent phagotrophic uptake of cryptomonads, so the presence of alloxanthin in D. norvegica may be a consistent feature of a permanent endosymbiosis.     

A PREHISTORIC BREEDING POPULATION OF HARP SEALS (PHOCA GROENLANDICA) IN THE BALTIC SEA

The pelagic and gregarious, low Arctic harp seal ( Phoca groenlandica ) is the most common seal species in most refuse faunas from coastal hunter-gatherer sites dating from the late Atlantic to the early Subboreal period ( ca. 4000-2000 cal B. C.) in the Baltic Sea. Our main objective was to examine the migration contra breeding population hypotheses regarding the Baltic harp seals. Analyses of epiphyseal fusion data and osteometry of archeological harp seal remains from 25 dwelling-sites suggest that a local breeding population established itself in the early Subboreal period. In the Middle Neolithic the rookery possibly was situated in the Baltic proper, south of Aland and west of Gotland. The mean adult size of the Baltic harp seals decreased, suggesting minimal genetic exchange with the north Atlantic Ocean population. Genetic drift, interspecific competition, and over-hunting by humans are all factors likely to have contributed to the eventual extinction of harp seals in the Baltic Sea.     

GENETIC AND MORPHOLOGICAL IDENTIFICATION OF FUCUS RADICANS SP. NOV. (FUCALES,PHAEOPHYCEAE) IN THE BRACKISH BALTIC SEA1

Brown seaweeds of the genus Fucus occupy a wide variety of temperate coastal habitats. The genus is evolutionary dynamic with recent radiations to form morphologically distinct taxa. In the brackish Baltic Sea, fucoids are the only perennial canopy‐forming macroalgae. The most northern populations of Fucus occur permanently submerged in extremely low salinity (3–5 psu). These are currently referred to as Fucus vesiculosus L. but are morphologically distinct with a narrow frond without bladders. We report here that a population of this unique morphotype is reproductively isolated from a truly sympatric population of common F. vesiculosus and conclude that the northern morphotype represents a previously undescribed species. We describe Fucus radicans sp. nov., which is attached and dioecious with broadly elliptic receptacles, characterized by a richly branched narrow flat frond (2–5 mm), short thallus (<26 cm), and a high capacity for vegetative recruitment of attached plants. Analysis of five highly polymorphic microsatellite DNA loci showed genetic differentiation between sympatric populations of F. radicans and F. vesiculosus, whereas allopatric populations of the same species revealed a coherent pattern of genetic variation. Sequences of the RUBISCO region in F. radicans were identical to or differing at only one to two dinucleotide positions from those of F. vesiculosus, indicating a recent common origin of the two species.     

陕北延长群一新古鳕类及其生物地层意义

本文记述了在陕西北部耀县铜川组发现的古鳕科一新属、种——延长三叠鳕(Triassodusyanchangensis,gen.et sp.nov.)。在对其形态特征作较详细描述的基础上,认为它既与美国晚三叠世的吐鲁瑟欧鳕(Turseodus)很接近,又与我国四川须家河组(晚三叠世)的蜀鳕(Sh-uniscus)相似。基于上述的理由,认为铜川组的时代是晚三叠世。根据迄今在我国晓三叠世发现的鱼类,探讨了我国晚三叠世的鱼群与北美的关系。     

GEOGRAPHICAL VARIATION OF THE PARASITE, PHYLLOBOTHRIUM DELPHINI (CESTODA), IN BALL'S PORPOISE, PHOCOENOIDES DALLI, IN THE NORTHERN NORTH PACIFIC, BERING SEA, AND SEA OF OKHOTSK

Prevalence of the larval cestode, Phyllobothrium delphini , was estimated from 2,445 Dall's porpoise, Phocoenoides dalli , from the incidental take of the Japanese high seas salmon drift-net fishery in the northwestern North Pacific Ocean, Bering Sea, and a local hand harpoon fishery in the southern Sea of Okhotsk. Prevalence of P. delphini was 22.7% in the northwestern North Pacific Ocean and 1.4% in the Bering Sea. This parasite was not found in the southern Sea of Okhotsk. Geographical differences in the prevalence of P. delphini may be due, at least in part, to regional differences in abundance of elasmobranchs known to feed on marine mammals and suspected as hosts of the parasite. Estimated intensity of infection of individual porpoises by P. delphini was low (estimated mean intensity of 3.5 plerocercoids per animal). This is a low intensity of infection compared to other species of small cetaceans studied and may be due to both differences in regional abundance of elasmobranchs and the comparatively short life span of P. dalli.